Positioning System and Method Thereof

ABSTRACT

The invention provides a positioning system. In one embodiment, the positioning system comprises a Global Navigation Satellite System (GNSS) module, a dead reckoning module, a Geographic Information System (GIS) module, and an calculating module. The GNSS module generates a first positioning data according to satellite communication. The dead reckoning module estimates a second positioning data according to a sensor&#39;s measurement data, the first positioning data, and a feedback positioning data of a previous epoch. The GIS module fits the first positioning data to a map to generate a third positioning data taken as a final output of the positioning system. The calculating module integrates the third positioning data and the second positioning data according to predetermined weights to obtain the feedback positioning data of a current epoch, which is recursively fed back to the dead reckoning module for a next estimation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of pending U.S. patent application Ser.No. 11/849,462, filed Sep. 4, 2007, the entirety of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to Global Navigation Satellite Systems (GNSS), andmore particularly to GNSS combined with dead reckoning system andGeographic Information System (GIS).

2. Description of the Related Art

GNSS is the standard generic term for satellite navigation systems thatprovide autonomous geo-spatial positioning with global coverage. GNSS isalso known as Global Positioning System (GPS) in the United States. AGNSS receiver determines its location comprising longitudes, latitudes,and altitudes according to radio signals transmitted from satellites. AGNSS receiver also calculates the precise time. Thus, a devicecomprising a GNSS receiver can easily obtain precise positioning data.For example, a driver can easily lead his car to destination accordingto navigation instruction of a GNSS device.

A GNSS device also has disadvantages. A few factors determines thequality of satellites communications. The number of visible satellitesin the sky determines the receiving quality of GNSS signals. Weatherconditions and signal receiving environments also greatly affect thequality of satellite communication. Because a GNSS receiver determinesits location according to radio signals sent by satellites, the GNSSreceiver cannot generate positioning data when satellite communicationfails. For example, when a car enters a tunnel, the receivingenvironment of the tunnel blocks the GNSS radio signals, and a GNSSdevice in the car cannot generate positioning data according to the GNSSsignals.

To determine a location when a GNSS device fails, a dead reckoningdevice is introduced in place of the GNSS device to temporarily estimatethe location. A dead reckoning device measures measurement thereof toestimate a location thereof. The dead reckoning device may be anaccelerometer measuring acceleration, an odometer measuring movingdistance, or a gyro measuring angular rate (compass measuring absoluteangles). The location estimation of a dead reckoning device, however,has greater errors and is usable only for a short period.

To solve the problem, the invention provides a positioning system whichcomprises a GNSS module, a dead reckoning module, and a GIS module. TheGIS module improves the precision of positioning data generated by theGNSS module and the dead reckoning module. Thus, the positioning systemprovides a location information with smaller error and can be usedlonger when the GNSS system fails.

BRIEF SUMMARY OF THE INVENTION

The invention provides a positioning system. In one embodiment, thepositioning system comprises a Global Navigation Satellite System (GNSS)module, a dead reckoning module, a GIS module, and a calculating module.The GNSS module generates a first positioning data according tosatellite communication. The dead reckoning module estimates a secondpositioning data according to a measurement data, the first positioningdata, and a feedback positioning data of a previous epoch. The GISmodule fits the first positioning data to a map to generate a thirdpositioning data taken as a final output of the positioning system. Thecalculating module uses the third positioning data and the secondpositioning data according to predetermined weights to obtain thefeedback positioning data of a current epoch, which is recursively fedback to the dead reckoning module for a next estimation.

The invention provides another positioning system. In one embodiment,the positioning system comprises a Global Navigation Satellite System(GNSS) module, a dead reckoning module, an calculating module, and a GISmodule. The GNSS module generates a first positioning data according tosatellite communication. The dead reckoning module estimates a secondpositioning data according to a measurement data, the first positioningdata, and a feedback positioning data of a previous epoch. Thecalculating module integrates the first positioning data and the secondpositioning data according to predetermined weights to obtain a thirdpositioning data. The GIS module fits the third positioning data to amap to generate the feedback positioning data of a current epoch, whichis taken as a final output of the positioning system and recursively fedback to the dead reckoning module for a next estimation.

The invention further provides another positioning system. In oneembodiment, the positioning system comprises a Global NavigationSatellite System (GNSS) baseband processor, a dead reckoning sensor, aKalman filter, and a GIS module. The GNSS baseband processor generates aGNSS measurement data according to satellite communication. The deadreckoning sensor generates a measurement data. The Kalman filterestimates a first positioning data according to the sensor's measurementdata, the GNSS measurement data, and a second positioning data of aprevious epoch. The GIS module fits the first positioning data to a mapto generate the second positioning data of a current epoch, which istaken as a final output of the positioning system and recursively fedback to the dead reckoning module for a next estimation.

The invention further provides a method of positioning. First, a GNSSmeasurement data is generated with a Global Navigation Satellite System(GNSS) baseband processor according to satellite communication. Ameasurement data is generated with a dead reckoning sensor. A firstpositioning data is then derived from the sensor's measurement data, theGNSS measurement data, and a feedback positioning data of a previousepoch when the first positioning data is available. The firstpositioning data is then fitted to a map with a GIS module to generate asecond positioning data of a current epoch, which is taken as a finaloutput of the positioning system. Finally, the second positioning datais recursively fed back as the feedback positioning data for derivationof the first positioning data of a next epoch.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a block diagram of a positioning system of a loosely-coupledmode according to the invention;

FIG. 2 is a block diagram of another positioning system of aloosely-coupled mode according to the invention;

FIG. 3 is a block diagram of a positioning system 300 of atightly-coupled mode according to the invention; and

FIG. 4 is a flowchart of a method of positioning according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIG. 1 is a block diagram of a positioning system 100 according to theinvention. The positioning system 100 comprises a GNSS module 102, adead reckoning module 104, a GIS module 106, and a calculating module108. The GNSS module 102 detects GNSS signals sent by satellites togenerate a positioning data S₁₁. In one embodiment, the positioning dataS₁₁ includes a position data, a velocity data, and a time data. The deadreckoning module 122 detects measurement thereof to generate apositioning data S₂₂. The GIS module 106 then adjusts the positioningdata S₁₁ according to a map data stored therein to obtain a positioningdata S₃, which is the final output of the positioning system 100. Thecalculating module 108 then averages the positioning data S₃ generatedby the GIS module 106 and the positioning data S₂₂ generated by the deadreckoning module 104 according to predetermined weights to obtain apositioning data S₄ as a feedback to the dead reckoning module 104.

The GNSS module 102 comprises a GNSS baseband processor 112 and a Kalmanfilter 114. The GNSS baseband processor 112 first generates GNSSmeasurement data S₁₀ according to satellite communication. The Kalmanfilter 114 then estimates the positioning data S₁₁ of a current epochaccording to both the GNSS measurement data S₁₀ of the current epoch andthe positioning data S₁₁ of a previous epoch. In one embodiment, theKalman filter also estimates the positioning data S₁₁ according to apositioning data S₂₁ provided by the dead reckoning module 104 inaddition to the GNSS measurement data S₁₀.

The dead reckoning module 104 comprises a dead reckoning sensor 122 anda Kalman filter 124. The dead reckoning sensor 122 generates ameasurement data of the positioning system. In one embodiment, the deadreckoning sensor 122 is a linear movement sensor measuring a linearmovement to generate the movement data, such as an accelerator measuringacceleration or an odometer measuring a moving distance. In anotherembodiment, the dead reckoning sensor 122 is an angular movement sensormeasuring an angular movement to generate the movement data, such as agyro measuring angular displacement or a compass measuring absoluteangles. In a further embodiment, the dead reckoning sensor 122 is theintegration of at least a linear movement sensor and an angular movementsensor.

The Kalman filter 124 comprises a time propagation module 126 and ameasurement update module 128. The time propagation module 126 estimatesa positioning data S_(21,T) of a current time T according to a feedbackpositioning data S_(4,T-1) of a previous time (T−1) and a measurementdata S_(20,T) of the current time T. Thus, the time propagation module126 carries out estimation based on a previous estimation dataS_(4,T-1). The measurement update module 128 then estimates apositioning data S_(22,T) of the current time T according to thepositioning data S_(21,T) of the current time T and the positioning dataS_(11,T) of the current time T. Thus, the measurement update module 128updates the estimation data S_(21,T) of the time propagation module 126according to the estimation data S_(11,T) generated by the GNSS module102.

The calculating module 108 generates the positioning data S₄ fed back tothe time propagation module 126 of the Kalman filter 124 of the deadreckoning module 104 for the estimation of the positioning data S₂₁. Thepositioning data S₄ is actually a weighted average of the positioningdata S₃ generated by the GIS module 106 and the positioning data S₂₂generated by the dead reckoning module 104. Because the positioning dataS₃ is generated according to the positioning data S₁₁ generated by theGNSS module 102 and the precision of the positioning data S₁₁ isdetermined by the quality of GNSS radio signals received fromsatellites, the precision of the positioning data S₃ greatly depends onthe quality of satellite communication of the GNSS module 102. Thus, thecalculating module dynamically adjusts the weights of the positioningdata S₃ and the positioning data S₂₂ according to the quality ofsatellite communication of the GNSS module 102 to improve the precisionof the positioning data S₄.

The quality of satellite communication of the GNSS baseband processor112 is determined by a few factors such as weather conditions, signalreceiving environments, and the number of visible satellites in the sky.When the quality of the satellite communication is too poor for the GNSSbaseband processor 112 to generate available GNSS measurement data S₁₀,the GNSS module 102 fails and no available positioning data S₁₁ isgenerated. Two modules, the GIS module 106 and the measurement updatemodule 128 require an input of the positioning data S₁₁. Thus, when thepositioning data S₁₁ is unavailable, the measurement update module 128of the Kalman filter 124 is disabled. In addition, the GIS module 106receives the positioning data S₂₁ as an input instead of the unavailablepositioning data S₁₁ and directly fits the positioning data S₂₁ to a mapdata to obtain the positioning data S₃. Thus, the positioning system 100can still generate an output positioning data S₃ while the GNSS module102 fails. Because the measurement update module 128 is disabled and nopositioning data S₂₂ is generated, the calculating module 108 directlyoutputs the positioning data S₃ generated by the GIS module 106 as thepositioning data S₄ as a feedback to the dead reckoning module 104.

If the Kalman filter 114 of the GNSS module 102 generates thepositioning data S₁₁ according to both the GNSS measurement data S₁₀ andthe positioning data S₂₁ generated by the time propagation module 126 ofthe dead reckoning module 104, the Kalman filter 114 can directlygenerate the positioning data S₁₁ according to only the positioning dataS₂₁ when the GNSS measurement data S₁₀ is unavailable. Thus, the GISmodule 106 can still fit the positioning data S₁₁ to a map data togenerate the positioning data S₃. Because the positioning data S₁₁ isgenerated according to positioning data S₂₁ generated by the deadreckoning module 104, the positioning data S₂₂ generated by themeasurement update module 128 is of no use due to unavailablemeasurement data S₁₀ and the calculating module 108 directly outputs thepositioning data S₃ generated by the GIS module 106 as the positioningdata S₄ as a feedback to the dead reckoning module 104.

FIG. 2 is a block diagram of another positioning system 200 according tothe invention. Similar to the positioning system 100, the positioningsystem 200 comprises a GNSS module 202, a dead reckoning module 204, ancalculating module 208, and a GIS module 206. The GNSS module 202 issimilar to the GNSS module 102 of FIG. 1, comprising a GNSS basebandprocessor 212 and a Kalman filter 214, and generating a positioning dataS₁₁. The dead reckoning module 204 is similar to the dead reckoningmodule 104 of FIG. 1, comprising a dead reckoning sensor 222 and aKalman filter 224, and generating a positioning data S₂₂.

The Kalman filter 224 of the dead reckoning module 204 comprises a timepropagation module 226 and a measurement update module 228. The timepropagation module 226 estimates a positioning data S_(21,T) of acurrent time T according to a feedback positioning data S_(6,T-1) of aprevious time (T−1) and a measurement data S_(20,T) of the current timeT. The measurement update module 228 then estimates a positioning dataS_(22,T) of the current time T according to the positioning dataS_(21,T) of the current time T and the positioning data S_(11,T) of thecurrent time T.

Different from the positioning system 100 of FIG. 1, the calculatingmodule 208 directly integrates the positioning data S₁₁ generated by theGNSS module 202 and the positioning data S₂₂ generated by the deadreckoning module 204 according to predetermined weights to obtain apositioning data S₅. The GIS module 206 then fits the positioning dataS₅ generated by the calculating module 208 to a map data stored thereinto generate a positioning data S₆, which is the final output of thepositioning system 200. The positioning data S₆ is then fed back to thetime propagation module 226 of the Kalman filter 224 of the deadreckoning module 204 for estimation of a next epoch.

The quality of satellite communication of the GNSS module 202 determineswhether available positioning data S₁₁ is generated. If no availablepositioning data S₁₁ is generated, the GIS module 206 only receives thepositioning data S₂₂ generated by the time propagation module 226 of thedead reckoning module 204 as an input and fits the positioning data S₂₂to a map data to generate the positioning data S₆ as the final output ofthe positioning system 200. In addition, if the Kalman filter 214 of theGNSS module 202 receives the positioning data S₂₂ generated by the timepropagation module 226 of the dead reckoning module 204 as an input, theKalman filter 214 can still generate an available positioning data S₁₁only according to the positioning data S₂₁ when the GNSS basebandprocessor 212 generates no available measurement data S₁₀ due to poorsatellite communication. In the situation, the calculating module 208then directly outputs the positioning data S₁₁ as the positioning dataS₅, and the GIS module 206 then fits the positioning data S₅ to a mapdata to generate the positioning data S₆ as the final output of thepositioning system 200.

FIGS. 1 and 2 shows positioning systems 100 and 200 categorized as aloosely coupled mode because the implementations involve two Kalmanfilters and each individual Kalman filter has its own specificparameters related ti specific inputs and also some common parameters.FIG. 3 is a block diagram of a positioning system 300 categorized as atightly coupled mode since only one Kalman filter is used and its statevector contains the parameters from GNSS and DR sensors according to theinvention. The positioning system 300 comprises a GNSS basebandprocessor 302, a dead reckoning sensor 304, a Kalman filter 306, and aGIS module 308. The GNSS baseband processor 302 generates a GNSSmeasurement data S₁ according to satellite communication. The deadreckoning sensor 304 detects measurement thereof to generate a sensor'smeasurement data S₂. The Kalman filter 306 then estimates a positioningdata S₈ according to the GNSS measurement data S₁, the sensor'smeasurement data S₂, and a feedback positioning data S₉ of a previousepoch. The GIS module 308 then fits the positioning data S₈ to a mapdata stored therein to generate the positioning data S₉ of a currentepoch, which is the final output of the positioning system 300. Thepositioning data S₉ is then recursively fed back to the Kalman filter306 for estimation of a next epoch.

The Kalman filter 306 comprises a time propagation module 312 and ameasurement update module 314. The time propagation module 312 firstestimates a positioning data S₇ of a current epoch according to the GNSSmeasurement data S₁ of the current epoch, the sensor's measurement dataS₂ of the current epoch, and the feedback positioning data S₉ of aprevious epoch. The measurement update module 314 then estimates thepositioning data S₈ of the current epoch according to the positioningdata S₇ of the current epoch. The measurement update module 314 isenabled only when the GNSS baseband processor 302 generates an availablemeasurement data S₁. When the GNSS baseband processor 302 fails due topoor satellite communication, the measurement update module 314 isdisabled, and the GIS module 308 receives the positioning data S₇generated by the time propagation module 312 instead of the positioningdata S₈ as an input to generate the final positioning data S₉. Thus, thepositioning system 300 can still generate a positioning data S₉ whilethe GNSS baseband processor 302 fails.

FIG. 4 is a flowchart of a method 400 of positioning according to theinvention. First, a GNSS measurement data is generated with a GNSSbaseband processor according to satellite communication in step 402. Ameasurement data is simultaneously generated with a dead reckoningsensor in step 404. If the GNSS measurement data is available in step406, a first positioning data is derived from the sensor's measurementdata, the GNSS measurement data, and a feedback positioning data of aprevious epoch in step 408. In the embodiment of FIG. 3, the firstpositioning data is derived by a single Kaliman filter 306. In theembodiment of FIG. 2, a third positioning data S₁₁ is estimatedaccording to the GNSS measurement data with a first Kalman filter 214,and a fourth positioning data S₂₂ is estimated according to the sensor'smeasurement data and the feedback positioning data of the previous epochwith a second Kalman filter 224, and the first positioning data S₅ isthen derived from the third positioning data S₁₁ and the fourthpositioning data S₂₂ according to predetermined weights.

Otherwise, if the GNSS measurement data is unavailable in step 406, thefirst positioning data is derived from the sensor's measurement data andthe feedback positioning data of the previous epoch in step 410. Thefirst positioning data is then fitted to a map with a GIS module togenerate a second positioning data of a current epoch in step 412. Thesecond positioning data is output as a final output in step 414.Finally, the second positioning data is recursively fed back as thefeedback positioning data for derivation of the first positioning dataof a next epoch in step 416.

The invention provides a positioning system comprising a GNSS module, adead reckoning module, and a GIS module. The positioning data generatedby the GNSS module and the dead reckoning module are combined togenerate a positioning data. In addition, the GIS module fits thepositioning data to a map data to generate a final positioning data withhigher precision. When the GNSS module fails due to poor satellitecommunication, the dead reckoning module can still generate ameasurement data. Because the final positioning data adjusted by the GISmodule has a higher precision and is fed back as a basis of a nextestimation, the estimation error of the dead reckoning module isreduced, and the final positioning data is more precise and therefore DRtime lasts longer in relative to the system without GIS aided.

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. To the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

1. A positioning system, comprising: a Global Navigation SatelliteSystem (GNSS) module, generating a first positioning data according tosatellite communication; a dead reckoning module, estimating a secondpositioning data according to a measurement data, the first positioningdata, and a feedback positioning data of a previous epoch; a calculatingmodule, deriving a third positioning data from the first positioningdata and the second positioning data according to predetermined weights;and a GIS module, fitting the third positioning data to a map togenerate the feedback positioning data of a current epoch, which istaken as a final output of the positioning system and recursively fedback to the dead reckoning module for a next estimation.
 2. Thepositioning system as claimed in claim 1, wherein the GNSS modulefurther comprises: a GNSS baseband processor, generating a GNSSmeasurement data according to satellite communication; and a firstKalman filter, coupled to the GNSS baseband processor, generating thefirst positioning data according to the GNSS measurement data.
 3. Thepositioning system as claimed in claim 1, wherein the dead reckoningmodule further comprises: a dead reckoning sensor, generating themeasurement data of the current epoch; and a second Kalman filter,coupled to the dead reckoning sensor, comprising: a time propagationmodule, estimating a fourth positioning data of the previous epoch andthe measurement data of the current epoch; and a measurement updatemodule, estimating the second positioning data of the current epochaccording to the fourth positioning data of the current epoch and thefirst positioning data of the current epoch.
 4. The positioning systemas claimed in claim 3, wherein the GIS module generates the feedbackpositioning data according to the fourth positioning data when the firstpositioning data is unavailable and the third positioning data iserroneous.
 5. The positioning system as claimed in claim 3, wherein theGNSS module comprises a first Kalman filter generating the firstpositioning data according to the fourth positioning data and a GNSSmeasurement data generated by a GNSS baseband processor.
 6. Thepositioning system as claimed in claim 5, wherein the first Kalmanfilter generates the first positioning data according to only the fourthpositioning data and the calculating module directly outputs the firstpositioning data as the third positioning data when the GNSS measurementdata is unavailable.
 7. The positioning system as claimed in claim 1,wherein the first positioning data comprises a position data, a velocitydata, and a time data.
 8. The positioning system as claimed in claim 3,wherein the dead reckoning sensor is the integration of at least alinear movement sensor measuring a linear movement to generate themeasurement data and an angular movement sensor measuring an angularmovement to generate the measurement data.